Bone conduction device

ABSTRACT

A bone conduction device which, when particularly employed in the receiver of a bone conduction telephone, is capable of obtaining a sufficient amount of sound as to not only a bone conduction sound but also an aerial vibration sound to ensure clear reception of the sound. The bone conduction device comprises a bone conduction device unit and a case receiving the device unit therein to serve as a vibration section and is characterized in that a compliance increasing means, such as a corrugation, is disposed along the peripheral edge of the vibrating surface of the case having the bone conduction device unit fixed thereto.

TECHNICAL FIELD

The present invention relates to a bone conduction device, and moreparticularly to a bone conduction speaker or a bone conductionmicrophone, wherein the bone conduction device is capable of keeping“loudness”, which is the properties of sound in volume of the deviceeven when the bone conduction device is not held in abutting contactwith the head portion of a user in use of a telephone set and likeinstruments in which the bone conduction device is incorporated.

BACKGROUND ART

For example, a bone conduction speaker is constructed of a boneconduction speaker unit 21 and a case 22 in which the speaker unit 21 ispackaged. The speaker unit 21 is constructed of: a doughnut-shaped voicecoil 24; a magnet 25 disposed on an inner peripheral surface of aperipheral wall 27 in a peripheral edge portion of a yoke 26; avibrating plate 28 mounted on an upper surface of the peripheral wall27; and, a vibrating block 29 fixedly mounted on an upper surface of thevibrating plate 28. The bone conduction speaker unit 21 has thevibrating block 29 thereof fixedly mounted on a ceiling surface in theinside of the case 22 through a screw 30 and like fastening means, sothat the speaker unit 21 is disposed inside the case 22 in construction(FIG. 4).

In such a construction, when the vibrating plate 28 vibrates, the case'svibrating surface on which the vibrating plate 28 is fixedly mountedthrough the vibrating block 29 also vibrates. Due to this, it ispossible for a user, even when the user is of advanced aged or hasdifficulty in hearing, to clearly catch the sound by bringing the case'svibrating surface into abutting contact with his or her head portion atthe side thereof behind the ear, or at the cheek or the forehead of thehead portion of the user so as to catch the sound as a bone conductionsound.

In the bone conduction speaker, which has such a construction and isbuilt in a telephone set, when the case's vibrating surface is separatedfrom the user's head portion, vibrations of the case's vibrating surfaceare then transmitted through air in the form of aerial vibrations, andbecome audible to the user through his or her eardrum just like ordinarysounds. Consequently, in case that people without disabilities use thebone conduction telephone set of this type, it is possible for thepeople without disabilities to avoid employing a cumbersome method,which forces the people without disabilities to keep the case'svibrating surface in a butting contact with their head portions in use,by employing the alternative method to the cumbersome method, in whichalternative method a receiver of the telephone set is disposed in thevicinities of their ears. However, heretofore, it is not possible forsuch alternative method to obtain a sufficient amount of aerialvibrations. Due to this, the problem lies in that the alternative methodis poor in “loudness” (i.e., the properties of sound in volume).

DISCLOSURE OF THE INVENTION

Since the conventional bone conduction speaker suffers from theabove-mentioned problem, it is an object of the present invention toprovide a bone conduction speaker, which is free from the probleminherent in the conventional bone conduction speaker. More particularly,it is an object of the present invention to provide a bone conductionspeaker, which is capable of producing a sufficient amount of soundvolume with respect to not only a bone conduction sound itself but alsoaerial vibrations when the bone conduction speaker is employed in areceiver of a bone conduction telephone set, thereby allowing the userto clearly catch the sound.

The present invention solves the above problem by providing a boneconduction device, which comprises: a bone conduction device unit; and,a case which receives the device unit therein to form a vibratingportion, and is characterized in that a compliance increasing means isso disposed as to extend along by a peripheral edge portion of avibrating surface of the case, wherein the bone conduction device unitis fixedly mounted on the vibrating surface of the case.

In general, the compliance increasing means is constructed of acorrugation. In this case, the corrugation may be a part ofmultiple-part corrugations.

Further, the compliance increasing means may be constructed of anelastic member. The elastic member may be different in material from thevibrating surface and disposed in the vibrating surface as a separatemember.

The compliance increasing means in the vibrating surface of the case mayhave its inner side formed into a spherical shape. Further, the case maybe constructed of a case of a telephone set.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a longitudinal sectional view of an embodiment of the boneconduction device (speaker) of the present invention.

FIG. 2 is an enlarged longitudinal sectional view of anther embodimentof the bone conduction device (speaker) of the present invention,illustrating an essential portion of the embodiment.

FIG. 3 is a graph illustrating a difference in lowest resonancefrequency between the case where the compliance increasing means isprovided and the other case where the compliance increasing means is notprovided.

FIG. 4 is a longitudinal sectional view of an example of theconventional bone conduction speaker.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to the accompanying drawings, embodiments of the presentinvention will be described. A bone conduction device of the presentinvention comprises a bone conduction speaker and a bone conductionmicrophone, both of which are substantially the same in construction.Due to this, only the bone conduction speaker will be describedhereinbelow.

FIG. 1 is a longitudinal sectional view of an embodiment of the boneconduction speaker of the present invention. FIG. 2 is an enlargedlongitudinal sectional view of anther embodiment of the bone conductionspeaker of the present invention, illustrating an essential portion ofthe embodiment. The bone conduction speaker of the present invention isconstructed of a bone conduction speaker unit 1 and a case 2 forpackaging the speaker unit 1 therein.

In general, the speaker unit 1 is constructed of: a doughnut-shapedvoice coil 4, which surrounds a central magnetic pole 3; a magnet 5disposed on an inner peripheral surface of a peripheral wall 7 in aperipheral edge portion of a yoke 6; a vibrating plate 8 mounted on anupper surface of the peripheral wall 7; and, a vibrating block 9 fixedlymounted on an upper surface of the vibrating plate 8. The boneconduction speaker unit 1 has the vibrating block 9 thereof fixedlymounted on a ceiling surface located in the inside of the case 2 througha screw 10 and like fastening means, so that the speaker unit 1 isdisposed inside the case 2 in construction

The above-mentioned construction is of a so-called “outer magnet” typeunit. In contrast with this type, it is also possible for the unit 1 toemploy a so-called “inner magnet” type construction, in which the magnet5 is disposed inside the voice coil 4.

A corrugation 12, which is small in thickness, is formed along aperipheral edge portion of a surface that is the vibrating surface 11 ofthe case 2, on which surface the vibrating block 9 is fixedly mounted.This corrugation 12 is a single corrugation as shown in FIG. 1, andfunctions to adequately increase in “compliance” of the vibratingsurface 11 (the term “compliance” is defined as the reciprocal of thestiffness). Shown in FIG. 2 are double corrugations, which may be usedin place of the single corrugation 12. The number of these corrugationsmay be further increased if necessary. Furthermore, it is also possibleto use an elastic member in place of the thin-thickness corrugation 12,which is different in material from the vibrating surface 11 anddisposed in the vibrating surface 11 as a separate member.

In the case where a person with difficulty in hearing uses a telephoneset which employs the bone conduction speaker having the aboveconstruction in its receiver portion, it is necessary for the personwith difficulty in hearing to hold the receiver of the telephone set inabutting contact with the ear in his or her head portion or in thevicinities of the ear of the head portion. In such a case, it ispossible to neglect in mass both of the case 2 and the vibrating plate 8in comparison with the mass of the head portion of the person. Due tothis, a lowest resonance frequency f₀, which determines a lower soundlimit of the speaker, is determined by: an effective mass M of avibrating system comprising the voice coil 4, magnet 5 and the yoke 6;and, a compliance C of the vibrating plate 8 which is an element forsupporting the above-mentioned vibrating system (see Equation 1).f ₀=1/(2π√{square root over ( )}M·√{square root over ( )}C)  [Equation1]

Incidentally, it is necessary to limit in value the compliance C of thevibrating plate 8 to an appropriate small level in order to ensurevariation in magnetic flax in a gap between the vibrating plate 8 andthe central magnetic pole 3, and further to ensure a sufficientstiffness of the vibrating plate 8 for keeping the above-mentioned gapagainst the weight of the bone conduction speaker unit 1. As a result,it is natural that the vibrating plate 8 is not capable of obtainingsufficient amplitude, and therefore has its frequency “f₀” kept at arelatively high level.

Further, even in the case where the person without disabilities use theabove-mentioned telephone set without bringing its receiver intoabutting contact with their head portions, the receiver is still held byhands of the person. Due to this, the Equation 1 is also applicable inthis case where: since the corrugation 12 provides a compliance C_(c),the lowest resonance frequency f_(0c) may be kept at a low level (seeEquation 2) and thereby permitting the inner area of the corrugation 12to obtain a sufficient amplitude, which results in an improvement in theproperties of sound pressure frequency. Due to this, a sufficient soundwave is easily issued from the bone conduction speaker to enable theperson to obtain a sufficient amount of sound volume.f _(0c)=1/(2π√{square root over ( )}M·√{square root over ( )}(C+C_(c)))  [Equation 2]

FIG. 3 is a graph, in which: the case (A) where the lowest resonancefrequency f₀ of the bone conduction speaker is not provided with thecorrugation 12 is compared with the other case (B) where the lowestresonance frequency f_(0c) of the bone conduction speaker is providedwith the corrugation 12, illustrating observed data. In comparison withthe case (A), it is recognized that the other case (B) according to thepresent invention is lower in lowest resonance frequencies.

In a cellular phone and like telephone sets which are required to bedownsized in both volume and weight, an effective mass M of the membersthereof comprising the voice coil 4, magnet 5 and the yoke 6 is small.Due to this, such a telephone set tends to keep its fundamentalfrequency in a relatively high frequency range. Consequently, in thiscase, an additional compliance derived from the provision of thecorrugation 12 is particularly effective.

Incidentally, although the case 2 is constructed of a case of thespeaker itself, it is also possible that the case 2 is constructed of acase of the telephone set. In the latter case, since the vibratingportion of the telephone set may be formed independently of theremaining members, the latter case is advantageous in this respect.

In anyone of the embodiments described above, it is preferable to formthe corrugation 12 or the elastic member, which is the alternative tothe corrugation 12, into a slightly projecting spherical shape (see FIG.2). Such a spherical shape makes it easy to bring the vibrating surface11 into abutting contact with the head portions of the users.

INDUSTRIAL APPLICABILITY

The present invention has a construction described in the above. Due tothis, in the bone conduction device of the present invention,particularly, in the bone conduction speaker of the present inventionemployed in the receiver of the bone conduction telephone set, it ispossible for the user to obtain a sufficient amount of the sound volumein each of the bone conduction sound and the aerial sounds, whichensures the user to be free from difficulties in hearing. It is alsopossible to directly apply the same construction of the bone conductionspeaker described above to a bone conduction microphone.

1. A bone conduction device comprising: a bone conduction device unit; and, a case which receives said device unit therein to form a vibrating portion, comprising: a compliance increasing means is so disposed as to extend along by a peripheral edge portion of a vibrating surface of said case, wherein said bone conduction device unit is fixedly mounted on said vibrating surface of said case.
 2. The bone conduction device as set forth in claim 1, wherein said compliance increasing means is constructed of a corrugation.
 3. The bone conduction device as set forth in claim 2, wherein said corrugation is a part of multiple-part corrugations.
 4. The bone conduction device as set forth in claim 1, wherein: said compliance increasing means is constructed of an elastic member; and, said elastic member is different in material from said vibrating surface and disposed in said vibrating surface.
 5. The bone conduction device as set forth in claim 1, wherein said compliance increasing means in said vibrating surface of said case has its inner side formed into a spherical shape.
 6. The bone conduction device as set forth in claim 1, wherein said case is constructed of a case of a telephone set.
 7. The bone conduction device as set forth in claim 1, wherein the bone conduction device takes the form of either a bone conduction speaker or a bone conduction microphone.
 8. The bone conduction device as set forth in claim 2, wherein said compliance increasing means in said vibrating surface of said case has its inner side formed into a spherical shape.
 9. The bone conduction device as set forth in claim 3, wherein said compliance increasing means in said vibrating surface of said case has its inner side formed into a spherical shape.
 10. The bone conduction device as set forth in claim 4, wherein said compliance increasing means in said vibrating surface of said case has its inner side formed into a spherical shape.
 11. The bone conduction device as set forth in claim 2, wherein the bone conduction device takes the form of either a bone conduction speaker or a bone conduction microphone.
 12. The bone conduction device as set forth in claim 3, wherein the bone conduction device takes the form of either a bone conduction speaker or a bone conduction microphone.
 13. The bone conduction device as set forth in claim 4, wherein the bone conduction device takes the form of either a bone conduction speaker or a bone conduction microphone.
 14. The bone conduction device as set forth in claim 5, wherein the bone conduction device takes the form of either a bone conduction speaker or a bone conduction microphone.
 15. The bone conduction device as set forth in claim 6, wherein the bone conduction device takes the form of either a bone conduction speaker or a bone conduction microphone.
 16. The bone conduction device as set forth in claim 8, wherein the bone conduction device takes the form of either a bone conduction speaker or a bone conduction microphone.
 17. The bone conduction device as set forth in claim 9, wherein the bone conduction device takes the form of either a bone conduction speaker or a bone conduction microphone.
 18. The bone conduction device as set forth in claim 10, wherein the bone conduction device takes the form of either a bone conduction speaker or a bone conduction microphone.
 19. The bone conduction device as set forth in claim 11, wherein the bone conduction device takes the form of either a bone conduction speaker or a bone conduction microphone. 